Could the Master be the new Doctor? That's what one newspaper is claiming. John Simm, who danced rings around David Tennant as the psycho arch-villain, is the "hot favorite" to play the Doctor when Tennant leaves. But it's unclear how the show could get around the fact that we saw Simm's body being cremated:

If Simm is to return in any guise, the show's writers would either have to explain his resurrection or add him in another way. And if he is indeed to return as the Doctor, an even more ingenious explanation will be required to account for his transformation from the Timelord's sworn enemy to the central character himself - unless, of course, their facial similarities are entirely glossed over.

Actually, the original Doctor Who already showed a Time Lord (Romana) regenerating into the doppleganger of someone she'd recently met. Maybe the Doctor's subconscious guilt that he couldn't save the Master will drive him to take on his face? A reality check is in order, however: it's probably way too early to be casting the next Doctor, since Tennant is set to play the role through 2009. But we can dream. In other news, Captain Jack will be in Doctor Who season four.
John Simm Tapped To Be New Doctor Who [IC Wales]